It is generally said that, in the sequela of cereblovascular diseases or various neuronal degenerative diseases, the dysfunction of cerebral neurons and the cerebral neuronal death are in a close relation. Particularly in the sequelae of cerebrovascular dementia, senile dementia, Alzheimer's disease and ischemic cerebral lesion and in the cerebral apoplexy, there appears memory impairment caused by a dysfunction of in-brain acetylcholine neurons or a selective neuronal death.
As drugs for symptomatic treatment of this memory impairment, for example, compounds having an acetylcholine esterase inhibiting activity such as Tacrine, Donepezil, and the like are used.
On the other hand, the anti-hypoxic activity is used for evaluating the neuroprotective activity in-vitro, and it is reported that, in the in-vivo experiments, too, compounds having a neuroprotective activity show the same effect as above [Ann. N. Y. Acad. Sci., Vol. 890, Pages 406-420, 1999]. Further, it has been reported that the anti-hypoxic activity is shown by compounds activating the in-brain acetylcholine neurons and by Tacrine (1,2,3,4-tetrahydro-9-acridinamine hydrochloride) showing an acetylcholine esterase inhibiting activity [Jpn. J. Pharmacol., Vol. 62, Pages 81-86, 1993].
Accordingly, a work for studying the in-vivo anti-hypoxic activity can be regarded as a method for evaluating the compounds having one of the neuroprotective effect and the in-brain acetylcholine neurons activating effect or both of these effects.
The 1,2-ethanediol derivatives or salts thereof described in JP 3-232830A and JP 4-95070A are compounds useful as a cerebral function-improving agent, and particularly (R)-1-{benzo[b]thiophen-5-yl}-2-[2-(N,N-diethylamino}ethoxy]ethanol hydrochloride (hereinafter, referred to as T-588) is a preferable compound. It has been reported that T-588 has an anti-hypoxic activity and an anti-amnestic activity, and promotes the release of in-brain acetylcholine (SOCIETY FOR NEUROSCIENCE, Abstracts, Vol. 21, Page 947, 1995). It is also known that T-588 exhibits a protecting effect on the neuronal death caused by amyloid-beta-protein (SOCIETY FOR NEUROSCIENCE, Abstracts, Vol. 24, Part 1, Page 228, 1998) and that T-588 exhibits an increasing effect on the action of nerve growth factor (WO96/12717). However, nothing has ever been reported with regard to the cerebral function improving action of T-588 and particularly to chemicals and method for improving the anti-hypoxic action thereof.
At the present time, compounds having a neuroprotective activity are being studied from the viewpoint of preventing the dysfunction of in-brain acetylcholine neurons or the selective neuronal death in the sequela of cerebrovascular dementia, senile dementia, Alzheimer's disease and ischemic cerebral lesion and in the cerebral apoplexy. However, the therapeutic effect of these compounds are not yet well known. Although acetylcholine esterase inhibiting drugs such as Tacrine, Donepezil, Galanthamine, and the like are commercially available as cerebral function-improving drugs including Alzheimer's disease-curing drug, these drugs have problems in the point of side-reactions because some of them have a hepatic toxicity and some others have a side reaction accompanied by activation of acetylcholine neurons other than central nervous system. Thus, for the purpose of lightening the side reaction of acetylcholine esterase inhibiting drugs, for example, a combination of a brain circulation metabolism improver such as Idebenone and an acetylcholine esterase inhibitor (JP 10-259126A) or a combination of a compound having a nerve growth factor-like activity (SR57746A) and an acetylcholine esterase inhibitor (WO99/25363), etc. are being attempted.